HYMENOPTERA 



313 



region. Unlike that of P. dryomyiae as described by Silvestri (1916), the 

 first polar body does not divide during the second maturation. Between 

 the tenth and twelfth hours the polar nucleus (the fused polar bodies) 

 increases in size to become the "paranuclear mass" (Fig. 260C). Just 

 before cleavage of the fusion nucleus the paranuclear mass divides 

 amitotically to form two subequal masses (Fig. 261 A). 



About the twenty-fourth hour two regions are recognized when the 

 central part of its posterior half becomes distinctly differentiated from the 

 remainder of the egg (Fig. 260C). This differentiated region contains 

 the fusion nucleus (cleavage nucleus) and is called the "embryonic 



nu.p 



emb- 



emb 



A B 



Fig. 261. — Platygaster. Parasitic body. A, about two days old. 5, three days old. (emb) 

 Embryonic region. i?iu. p) Paranuclear masses. 



region," later giving rise to the embryos. The remainder of the egg con- 

 taining the polar nucleus constitutes the polar region. Between the first 

 and second days the eggs, five to eight in number, deposited by the 

 parasite in the host become somewhat dispersed throughout the develop- 

 ing host if they were deposited in the host egg. If the eggs were deposited 

 in a well-developed embryo of the host or in a recently hatched host larva^, 

 they become scattered in the body cavity of the host at an earlier hour. 

 The eggs begin to increase in size soon after the first day, and therefore the 

 egg stage may be regarded as past ; henceforth the developing structures 

 may be regarded as parasite bodies. These are lodged in the salivary 

 glands, fat, or other host tissue, portions of which soon encompass the 

 parasite bodies. After being more or less surrounded by host tissue, an 

 elaboration of the paranuclear masses in the polar region takes place by 

 the absorption of substances from the host. The polar region, including 



